Wireless access networks, including cellular networks, are designed for providing user connectivity with the Internet or with multimedia servers. The Internet is considered to be the main source of information for mobile users.
Cellular base stations will become more service oriented, some of them already providing cashing services for video streamed by the network. Adding services to base stations is perceived as an IaaS (Infrastructure as a Service) approach, providing additional revenues for the cellular operators.
Video streaming is an example of multimedia services. Due to capacity limitations of the transport network, the video is compressed in compliance with International Standards, for example MPEG-2 or MPEG-4. There are two main aspects of a compressed video image, which have adverse effects on a possible implementation:
1. Quality, the image being slightly distorted due to compression;
2. Latency, resulting from the relatively long time required for compression and decompression (only the compression step may take 500 ms).
The CEA-861 and the HDMI (High Definition Media Interface) standards define video frame formats for uncompressed high definition video, wherein the data rates required for uncompressed image transmission vary between 0.5 Gb/s and 3 Gb/s. The wireless video transmission at such high data rates is possible by using either 802.11, LTE or proprietary solutions. With few exceptions, the users of such systems are fixed and indoor located. The few cases in which the users are mobile, outdoor located, involve industrial applications, but these do not use yet the cellular technology.
For each pixel a color code may be transmitted according to standard formats (e.g. RGB, YCbCr, etc.). The color code includes the number of bits used for each color or luma (brightness) component.
The mobile service enables “applications”, running on the mobile phone. The modern cellular systems, like LTE, provide support for broadcast compressed video, the related functionality being known as MBSFN (Multi Media Broadcast Single Frequency Network), targeting the video service via a multitude of base stations which operate in a synchronized mode and transmit the compressed video image.
“Video over IP”, is another video streaming service, which is in fact a data service, using also compressed video.